In modern multistage gas turbines, the first several rows of stationary vanes must be cooled with a fluid in order to maintain their structural capability. In these turbines, compressed air is taken from an extraction point on a compressor and supplied to cool the vanes and then is discharged. U.S. Pat. No. 3,945,758, which is assigned to the assignee of the present invention, discloses a turbine having rows of stationary vanes radially extending from seal housings disposed about a rotor adjacent to rows of blades mounted on the rotor structure. Each vane in the later rows has a central elongated airfoil body disposed between an outer shroud attached to a casing and an inner shroud attached to a seal housing. Coolant fluid flows from a source of supply through passages and cavities into inlets in the outer shroud, radially inwardly through parallel channels in the airfoil body and outlets in the inner shroud and then into a chamber generally defined by the inner shroud and the seal housing. The coolant fluid in the chamber cooling the inner shroud and the seal housing then leaks into the hot gases flowing through the turbine around the inner shroud. A portion of the coolant fluid in the chamber leaks through clearance spaces between the seal and the rotor to protect the seal and rotor. U.S. Pat. No. 4,684,322 discloses a different coolant system wherein the coolant fluid is discharged via ports in the airfoil body directly into the hot gases flowing through the turbine. In both of these types of coolant systems, the system is primarily designed to cool the vanes.
It is an object of the present invention to provide a cooled turbine vane having a coolant system for protecting the vane and a second coolant system for protecting the seal and its housing. It is a further object of the present invention to improve the overall efficiency of the turbine by providing the coolant fluid to the vane in smaller quantities and at lower pressures.